Discretized Discontinuous Modulation Strategy for Cascaded H-Bridge StatCom

This article proposes a discontinuous modulation (DM) scheme for cascaded H-bridge static compensators with star configuration. The proposed DM scheme guarantees zero steady-state active power in each converter phase arm, even in the presence of severe grid imbalance conditions, thus remaining decoupled from the interphase capacitor voltage balancing controller. Moreover, the proposed DM scheme exploits the possibility of clamping to the zero-voltage level, thus providing a more flexible discontinuous operation than conventional DM methods. This involves lower zero-sequence-voltage injection requirements and lower switching losses. The proposed modulation scheme is experimentally corroborated, and its performance under different grid voltage conditions is compared with traditional modulation schemes.